The cochlear implant is a neural prosthetic device that provides a perception of hearing and facilitates communication for persons who are profoundly deaf. Speech and sound information is transformed into electrical signals that create a perception of sound upon their application to fibers of the auditory nerve within the cochlea. The device is intended for persons with profound sensorineural deafness. This condition exists when the sensory hair cells of the organ of Corti are disabled while fibers of the auditory nerve and their connection in the central nervous system remain functionally intact. The electrical stimuli that are applied within the cochlea are then appropriately conveyed and interpreted as audible information. Cochlear prostheses are designed to stimulate the auditory nerve in a manner that exploits the ability of the cochlea and central nervous system to discriminate the frequency, tempo aditensity. of ambient sound in ways that assist the wearer to recognize ItS source and information content. Selection of candidates for implantation involves confirmation of profound bilateral sensorineural deafness that cannot be mitigated by the use of a modern powerful hearing aid capable of providing benefits equal to those obtainable from an implant. In addition, the cognitive ability to make use of auditory clues, and the willingness to conscientiously pursue an extended program of aural/visual rehabilitation, must be present. Patients who have become deaf after developing normal language skills are most amenable to implantation since sound recognition is aided by established associations and memory.